One space between each sentence, they said. Science just proved them wrong.

In the beginning, the rules of the space bar were simple. Two spaces after each period. Every time. Easy.

That made sense in the age of the typewriter. Letters of uniform width looked cramped without extra space after the period. Typists learned not to do it.

But then, at the end of the 20th century, the typewriter gave way to the word processor, and the computer, and modern variable-width fonts. And the world divided.

Some insisted on keeping the two-space rule. They couldn't get used to seeing just one space after a period. It simply looked wrong.

Some said this was blasphemy. The designers of modern fonts had built the perfect amount of spacing, they said. Anything more than a single space between sentences was too much.

And so the rules of typography fell into chaos. “Typing two spaces after a period is totally, completely, utterly, and inarguably wrong,” Farhad Manjoo wrote in Slate in 2011. “You can have my double space when you pry it from my cold, dead hands,” Megan McArdle wrote in the Atlantic the same year. (And yes, she double-spaced it.)

This schism has actually existed throughout most of typed history, the writer and type enthusiast James Felici once observed (in a single-spaced essay).

The rules of spacing have been wildly inconsistent going back to the invention of the printing press. The original printing of the U.S. Declaration of Independence used extra long spaces between sentences. John Baskerville's 1763 Bible used a single space. WhoevenknowswhateffectPietroBembowasgoingforhere.Single spaces. Double spaces. Em spaces. Trends went back and forth between continents and eras for hundreds of years, Felici wrote.It's not a good look.

They cite dozens of theories and previous research, arguing for one space or two. A 2005 study that found two spaces reduced lateral interference in the eye and helped reading. A 2015 study that found the opposite. A 1998 experiment that suggested it didn't matter.

“However,” they wrote, “to date, there has been no direct empirical evidence in support of these claims, nor in favor of the one-space convention.”

So the researchers, Rebecca L. Johnson, Becky Bui and Lindsay L. Schmitt, rounded up 60 students and some eye-tracking equipment, and set out to heal the divide.

First, they put the students in front of computers and dictated a short paragraph, to see how many spaces they naturally used. Turns out, 21 of the 60 were “two-spacers,” and the rest typed with close-spaced sentences that would have horrified the Founding Fathers.

The researchers then clamped each student's head into place, and used an Eyelink 1000 to record where they looked as they silently read 20 paragraphs. The paragraphs were written in various styles: one-spaced, two-spaced, and strange combinations like two spaces after commas, but only one after periods. And vice versa, too.

And the verdict was: two spaces after the period is better. It makes reading slightly easier. Congratulations, Yale University professor Nicholas A. Christakis. Sorry, Lifehacker.

Actually, Lifehacker's one-space purist Nick Douglas pointed out some important caveats to the study's conclusion.

Most notably, the test subjects read paragraphs in Courier New, a fixed-width font similar to the old typewriters, and rarely used on modern computers.

Johnson, one of the authors, told Douglas that the fixed-width font was standard for eye-tracking tests, and the benefits of two-spacing should carry over to any modern font.

Douglas found more solace in the fact that the benefits of two-spacing, as described in the study, appear to be very minor.

Reading speed only improved marginally, the paper found, and only for the 21 “two-spacers,” who naturally typed with two spaces between sentences. The majority of one-spacers, on the other hand, read at pretty much the same speed either way. And reading comprehension was unaffected for everyone, regardless of how many spaces followed a period.

The major reason to use two spaces, the researchers wrote, was to make the reading process smoother, not faster. Everyone tended to spend fewer milliseconds staring at periods when a little extra blank space followed it.

(Putting two spaces after a comma, if you're wondering, slowed down reading speed, so don't do that.)

The study's authors concluded that two-spacers in the digital age actually have science on their side, and more research should be done to “investigate why reading is facilitated when periods are followed by two spaces.”

But no sooner did the paper publish than the researchers discovered that science doesn't necessarily govern matters of the space bar.

Johnson told Lifehacker that she and her co-authors submitted the paper with two spaces after each period — as was proper. And the journal deleted all the extra spaces anyway.

Note: An earlier version of this story published incorrectly because, seriously, putting two spaces in the headline broke the web code.

Content from Allstate This content is paid for by an advertiser and published by WP BrandStudio. The Washington Post newsroom was not involved in the creation of this content. Learn more about WP BrandStudio.